CN114069041A - Viscoelastic electrolyte modification layer and preparation method and application thereof - Google Patents

Viscoelastic electrolyte modification layer and preparation method and application thereof Download PDF

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CN114069041A
CN114069041A CN202111347490.9A CN202111347490A CN114069041A CN 114069041 A CN114069041 A CN 114069041A CN 202111347490 A CN202111347490 A CN 202111347490A CN 114069041 A CN114069041 A CN 114069041A
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electrolyte
viscoelastic
modification layer
pole piece
solid
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陈规伟
高强强
冀亚娟
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Eve Energy Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a viscoelastic electrolyte modification layer and a preparation method and application thereof. The viscoelastic electrolyte modification layer comprises, by mass, 45-65% of succinonitrile, 5-25% of a polymer substrate and 20-40% of lithium salt. The electrolyte modification layer is uniformly coated on the surface of the pole piece and then assembled with the solid electrolyte to obtain the all-solid-state battery. The electrolyte modification layer can penetrate into the electrode layer to provide a lithium ion diffusion channel in the layer; connecting the positive electrode with the electrolyte interface, and eliminating the possible gap at the interface; providing a lithium ion diffusion channel between the positive electrode and the electrolyte; the volume change stress of the positive electrode active material is borne, and interface degradation caused by the volume change is avoided.

Description

Viscoelastic electrolyte modification layer and preparation method and application thereof
Technical Field
The invention relates to the field of lithium ion batteries, relates to a solid-state battery, and particularly relates to a viscoelastic electrolyte modification layer, and a preparation method and application thereof.
Background
The domestic electric vehicle market is developed rapidly due to a series of national subsidy policies for the electric vehicle industry. The energy density of the single battery reaches 400-500Wh/kg by 2025 and 2030, but the energy density and the safety performance of the battery after 2025 cannot meet the national requirements based on the existing liquid electrolyte lithium ion power battery system. The use of a nonflammable solid electrolyte instead of a conventional liquid electrolyte can increase the energy density of the battery by about 66% while securing the safety performance of the battery, and thus the solid battery is considered to be an important direction of the next-generation battery technology.
At present, the solid-state battery cannot be applied to commercialization and scale production because of a series of interface problems. For solid-state batteries, the interface problems can be divided into four categories: (1) solid electrolytes are not very electrochemically and chemically stable. The solid electrolyte needs to simultaneously meet the requirements of electrical property, chemical property, physical property and cost, and no solid electrolyte can meet the requirements at present. At present, the electrochemical windows of solid electrolytes with higher ionic conductivity, such as sulfide electrolytes and oxide electrolytes, are narrow, so that the application of high-voltage anode materials and lithium metal cathodes is difficult to meet. The stability of the sulfide electrolyte and the polymer electrolyte to the lithium metal negative electrode is poor, so that the improvement of the energy density of the battery is limited; (2) the electrode and electrolyte interface contact is poor. Because the electrode and the electrolyte are both in a solid state, when the electrode and the electrolyte are contacted, a large number of gaps exist at the interface, the transmission of lithium ions is blocked, and the interface degradation is accelerated, so that the electrical property of the solid-state battery at the present stage is far from being compared with that of the traditional electrolyte battery; (3) the stress at the electrode and electrolyte interface changes. Active materials of the electrode, such as LCO, C, etc., undergo volume expansion during charge and discharge. For a solid electrolyte interface in solid-solid contact, the volume expansion can cause a series of problems such as SEI film rupture at the interface, solid electrolyte fragmentation and the like; (4) the electrode having a high active material content lacks an ion conductor inside, and lithium ion diffusion is difficult. In order to improve the energy density of a battery cell, the active substance proportion of the current commercialized positive pole piece is generally 95-98%, and the energy density of the battery cell is reduced due to the additional addition of an ion conductor, so that a good ion transmission channel cannot be constructed in the electrode; there are currently a number of approaches to solving the solid-state battery interface problem. The most common method is to add a small amount of electrolyte at the interface of the solid-state battery or solidify the electrolyte in situ to prepare the solid-liquid hybrid battery so as to improve the interface problem.
CN111509186B discloses a method for directly coating a polymer electrolyte on the surface of a pole piece to form a solid electrolyte membrane, wherein the solid electrolyte glue solution penetrates into the positive and negative pole pieces during the coating process to provide ion conductivity, and the dried electrolyte and the electrode are tightly attached to avoid the occurrence of interface voids. And the polymer electrolyte has good flexibility and can bear the volume change stress generated in the charge and discharge processes of the active material. However, the method is limited by the current coating technology, when the coating is too thin, the stability of the coating is affected, meanwhile, in the coating process, too high solid content is not beneficial to reducing the thickness of the coating, and too low solid content is not beneficial to the stability of the coating, so that the uniformity of the coating is ensured. This method is therefore technically difficult to implement. In addition, methods for constructing a modification layer at an interface by methods such as sputtering, spin coating, electrostatic spraying and the like exist, and the method has the problem that large-scale application is difficult.
CN104241686A discloses an all-solid-state composite electrolyte membrane, and the specific scheme is as follows: polyethylene oxide (PEO), inorganic filler and lithium salt are used as raw materials, and an all-solid-state electrolyte with high conductivity (>10s/CM), good viscoelasticity and plasticity is obtained by a solution blending method through controlling the molecular weight of an organic high polymer, the diameter and the shape of the inorganic filler, the type, the component proportion and the synthesis condition of the lithium salt; the prepared electrolyte and microporous membrane are dipped and dried in vacuum to obtain the all-solid-state composite electrolyte membrane with viscoelasticity on the surface and good mechanical strength in the center. The disclosed invention improves the safety performance of the electrolyte membrane, also solves the impedance problem in the interface between the electrolyte and the electrode, but has no beneficial effect on the stress change at the interface between the electrode and the electrolyte.
CN111525188A discloses a PEO-PMMA solid electrolyte membrane, which comprises a plurality of electrolyte matrix layers arranged in a layered overlapping mode, wherein the electrolyte matrix layers are combined and cured into a whole, each electrolyte matrix layer is a solid mixture obtained by uniformly mixing and fusing a plurality of same raw materials, the raw materials comprise PEO, PMMA, inorganic lithium salt, a plasticizer and an inorganic solid particle material, and the hardness of each electrolyte matrix layer is arranged layer by layer from low to high. The solid electrolyte membrane provided by the invention has good safety performance, stability and good interface compatibility, and simultaneously has excellent mechanical property and conductivity, but the improvement degree of the electrochemical property and the interface compatibility of PEO-PMMA is limited, and the cycle stability also needs to be further improved.
As can be seen from the above explanation, the interface modification layer is very important to solve the interface problem of the solid-state battery, and how to prepare a solid-state battery with good interface performance is an important research direction in the field.
Disclosure of Invention
The invention aims to provide a viscoelastic electrolyte modification layer, and a preparation method and application thereof. The viscoelastic electrolyte modifying layer has good interfacial properties.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention aims to provide a viscoelastic electrolyte modification layer, which comprises, by mass, 45-65% of succinonitrile, 5-25% of a polymer substrate and 20-40% of lithium salt.
The mass fraction of the succinonitrile may be 45%, 47%, 49%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 65%, etc., the mass fraction of the polymer base may be 5%, 7%, 9%, 11%, 12%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, etc., and the mass fraction of the lithium salt may be 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, etc., but is not limited to the values listed, and other values not listed in the above numerical ranges are also applicable.
The invention provides a viscoelastic electrolyte modification layer which is composed of succinonitrile, a polymer substrate and lithium salt, wherein the succinonitrile and the lithium salt provide high ionic conductivity, and the polymer substrate and the succinonitrile are combined to form a viscoelastic material. And uniformly coating the electrolyte modification layer on the surface of the pole piece, and then assembling the electrolyte modification layer with the solid electrolyte to obtain the all-solid-state battery. The electrolyte modification layer can penetrate into the electrode layer to provide an in-layer lithium ion diffusion channel; connecting the positive electrode with the electrolyte interface, and eliminating the possible gap at the interface; providing a lithium ion diffusion channel between the positive electrode and the electrolyte; the volume change stress of the positive electrode active material is borne, and interface degradation caused by the volume change is avoided.
As a preferred embodiment of the present invention, the polymer substrate includes any one or a combination of at least two of PEO, derivatives of PEO, PMMA, derivatives of PMMA, PVDF, derivatives of PVDF, PPC, derivatives of PPC, PVC or derivatives of PVC, wherein typical but non-limiting examples of the combination are a combination of PEO and derivatives of PEO, a combination of PMMA and derivatives of PMMA, a combination of PVDF and derivatives of PVDF, a combination of PPC and derivatives of PPC, a combination of PVC and derivatives of PVC, a combination of PEO and derivatives of PMMA, a combination of PPC and derivatives of PVC, and the like.
As a preferred technical scheme of the invention, the lithium salt comprises LiTFSI, LiFSI and LiPF6LiBOB, LiODFB or LiClO4Any one or a combination of at least two of the above, typical but non-limiting examples of which are the combination of LiTFSI and LiFSI, LiPF6And LiBOB, LiODFB and LiClO4A combination of LiTFSI and LiBOB, a combination of LiBOB and LiODFB, or the like.
Another object of the present invention is to provide a method for producing a viscoelastic electrolyte modification layer according to the first object, the method comprising:
adding the raw materials of the viscoelastic electrolyte modification layer into an organic solvent for mixing to obtain a viscoelastic electrolyte glue solution;
and respectively and independently coating the viscoelastic electrolyte glue solution on the surfaces of the positive pole piece and the negative pole piece, and respectively and independently obtaining viscoelastic electrolyte modification layers on the surfaces of the positive pole piece and the negative pole piece after drying.
As a preferred embodiment of the present invention, the organic solvent includes any one or a combination of at least two of acetonitrile, N-dimethylformamide, acetone, chloroform, anisole or dichloroethane, and typical but non-limiting examples of the combination are: a combination of acetonitrile and N, N-dimethylformamide, a combination of N, N-dimethylformamide and acetone, a combination of acetone and chloroform, a combination of chloroform and anisole, a combination of anisole and dichloroethane, or the like.
Preferably, the raw material of the electrolyte modification layer accounts for 5-20% of the solid content of the organic solvent, wherein the solid content may be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
In a preferred embodiment of the present invention, the mixing speed is 500 to 1000rpm, and the mixing speed may be 500rpm, 550rpm, 600rpm, 650rpm, 700rpm, 750rpm, 800rpm, 850rpm, 900rpm, 950rpm, 1000rpm, or the like, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable.
Preferably, the mixing time is 10-15 h, wherein the time can be 10h, 11h, 12h, 13h, 14h or 15h, etc., but is not limited to the recited values, and other values not recited in the range of values are also applicable.
In a preferred embodiment of the present invention, the coating thickness of the surface of the positive electrode sheet is 3 to 10 μm, wherein the thickness may be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.
Preferably, the coating thickness of the surface of the negative electrode plate is 5-12 μm, wherein the thickness can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm or 12 μm, but is not limited to the enumerated values, and other values in the numerical range are also applicable.
In a preferred embodiment of the present invention, the drying temperature is 60 to 80 ℃, wherein the temperature may be 60 ℃, 62 ℃, 64 ℃, 66 ℃, 68 ℃, 70 ℃, 72 ℃, 74 ℃, 76 ℃, 78 ℃ or 80 ℃, but is not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
Preferably, the drying time is 6-12 h, wherein the drying time can be 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc., but is not limited to the recited values, and other values not recited in the range of the values are also applicable.
It is a further object of the present invention to provide an all-solid battery including the viscoelastic electrolyte modification layer according to one of the objects.
Preferably, the all-solid-state battery comprises a positive electrode plate containing the viscoelastic electrolyte modification layer, a negative electrode plate containing the viscoelastic electrolyte modification layer and a solid electrolyte.
The raw materials of the positive pole piece comprise 90-98% of positive active material, 0.5-5% of conductive agent and 1.5-5% of binder according to mass fraction.
Wherein the mass fraction of the positive electrode active material may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc., the mass fraction of the conductive agent may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., and the mass fraction of the binder may be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., but is not limited to the recited values, and other values not recited in the above-mentioned numerical ranges are also applicable.
Preferably, the solid content of the raw material of the positive electrode sheet in the positive electrode solvent is 30-80%, wherein the solid content may be 30%, 40%, 50%, 60%, 70%, or 80%, but is not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
Preferably, the positive electrode solvent includes any one of N, N-dimethylformamide, N-methylpyrrolidone or dimethylacetamide, or a combination of at least two thereof, as typical but non-limiting examples: a combination of N, N-dimethylformamide and N-methylpyrrolidone, a combination of N-methylpyrrolidone and dimethylacetamide, a combination of N, N-dimethylformamide and dimethylacetamide, or the like.
Preferably, the positive electrode active material includes any one of a ternary material, lithium iron phosphate, lithium manganate or lithium cobaltate or a combination of at least two thereof, wherein typical but non-limiting examples thereof are a combination of a ternary material and lithium iron phosphate, a combination of lithium iron phosphate and lithium manganate or a combination of lithium manganate and lithium cobaltate, and the like.
Preferably, the conductive agent comprises any one of conductive carbon black, conductive graphite, carbon fiber or carbon nanotube or a combination of at least two of them, wherein typical but non-limiting examples of the combination are a combination of conductive carbon black and conductive graphite, a combination of conductive graphite and carbon fiber, a combination of carbon fiber and carbon nanotube or a combination of conductive graphite and carbon nanotube, and the like.
Preferably, the binder includes any one of polyvinyl alcohol, polyacrylic acid, styrene-butadiene rubber, or sodium carboxymethylcellulose, or a combination of at least two thereof, wherein typical but non-limiting examples thereof are a combination of polyvinyl alcohol and polyacrylic acid, a combination of polyacrylic acid and styrene-butadiene rubber, a combination of polyacrylic acid and sodium carboxymethylcellulose, or a combination of polyvinyl alcohol and styrene-butadiene rubber, and the like.
The cathode plate comprises, by mass, 90-98% of a cathode active material, 0.5-5% of a conductive agent and 1.5-5% of a binder.
Wherein the mass fraction of the negative electrode active material may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc., the mass fraction of the conductive agent may be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., and the mass fraction of the binder may be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., but is not limited to the recited values, and other values not recited in the above-mentioned numerical ranges are also applicable.
Preferably, the solid content of the raw material of the negative electrode sheet in the negative electrode solvent is 40-60%, wherein the solid content may be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, etc., but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.
Preferably, the negative electrode solvent comprises deionized water.
Preferably, the anode active material includes any one of a silicon oxygen anode material, a silicon carbon anode material, or a tin carbon anode material.
Preferably, the conductive agent comprises any one of conductive carbon black, conductive graphite, carbon fiber or carbon nanotube or a combination of at least two of them, wherein typical but non-limiting examples of the combination are a combination of conductive carbon black and conductive graphite, a combination of conductive graphite and carbon fiber, a combination of carbon fiber and carbon nanotube or a combination of conductive graphite and carbon nanotube, and the like.
Preferably, the binder comprises any one of polyvinyl alcohol, polyacrylic acid, styrene butadiene rubber or sodium carboxymethyl cellulose or a combination of at least two of the two. Typical but non-limiting examples of such combinations are a combination of polyvinyl alcohol and polyacrylic acid, a combination of polyacrylic acid and styrene-butadiene rubber, a combination of polyacrylic acid and sodium carboxymethylcellulose or a combination of polyvinyl alcohol and styrene-butadiene rubber, and the like.
The solid electrolyte in the present invention includes any one of a polymer solid electrolyte, an organic composite solid electrolyte, an inorganic composite solid electrolyte, an oxide electrolyte or a sulfide electrolyte.
The positive pole piece, the negative pole piece and the solid electrolyte are all conventional materials and are not limited too much.
The fourth purpose of the present invention is to provide an application of the viscoelastic electrolyte modification layer, wherein the viscoelastic electrolyte modification layer is applied to the field of lithium ion batteries.
Compared with the prior art, the invention has the following beneficial effects:
(1) the viscoelastic electrolyte modification layer has certain fluidity, can penetrate into the pole piece to provide an ion transmission network, and has the ion conductivity of 7 multiplied by 10-4S cm-1The above. The discharge capacity of the first ten circles can reach more than 22.4 mAh;
(2) the viscoelastic electrolyte modification layer can bond the anode and the cathode with the solid electrolyte, so that physical and chemical contact is improved;
(3) the viscoelastic electrolyte modification layer can bear stress change at the interface, so that the interface degradation phenomenon is relieved;
(4) the viscoelastic electrolyte modification layer is non-combustible, so that the safety performance of the battery cell can be effectively improved.
Drawings
Fig. 1 is a viscoelastic interface modified battery discharge capacity in example 1 of the present invention.
Fig. 2 is a structural view of a solid-state battery in comparative example 5 of the present invention.
Fig. 3 is a structural view of a solid-state battery in examples 1 to 11 of the present invention and comparative examples 1 to 4.
In the figure: 1-positive pole piece; 2-negative pole piece; 3-a viscoelastic electrolyte modifying layer; 4-solid electrolyte.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
This example provides a method for preparing a viscoelastic electrolyte modification layer:
weighing the following raw materials in parts by mass: succinonitrile 55%, PEO substrate 15%, LiTFSI 30%. The raw materials are dissolved in acetonitrile, the solid content is controlled to be 13%, and the mixture is stirred for 12 hours to obtain the required viscoelastic solid electrolyte glue solution. Taking the cut positive pole piece, and uniformly coating the glue solution on the surface of the positive pole piece by using a wire rod, wherein the coating thickness is controlled to be 6.5 mu m. Similarly, a layer of glue solution is coated on the surface of the negative pole piece, and the coating thickness is controlled to be 9 μm. And then placing the pole piece coated with the viscoelastic electrolyte glue solution at 70 ℃ for vacuum drying for 9 hours to obtain the modified pole piece. The discharge capacity of the cell containing the viscoelastic electrolyte modified layer of this example is shown in fig. 1.
Example 2
This example provides a method for preparing a viscoelastic electrolyte modification layer:
weighing the following raw materials in parts by mass: 45% of succinonitrile, 25% of PMMA substrate and 30% of LiFSI. The raw materials are dissolved in N, N-dimethylformamide, the solid content is controlled to be 5%, and the required viscoelastic solid electrolyte glue solution is obtained after stirring for 15 hours. And (3) taking the cut positive pole piece, and uniformly coating the glue solution on the surface of the positive pole piece by using a wire rod, wherein the coating thickness is controlled to be 3 micrometers. Similarly, a layer of glue solution is coated on the surface of the negative pole piece, and the coating thickness is controlled to be 5 μm. And then placing the pole piece coated with the viscoelastic electrolyte glue solution at 60 ℃ for vacuum drying for 12h to obtain the modified pole piece.
Example 3
This example provides a method for preparing a viscoelastic electrolyte modification layer:
weighing the following raw materials in parts by mass: succinonitrile 65%, PVDF substrate 15%, LiPF 620 percent. The raw materials are dissolved in N, N-dimethylformamide, the solid content is controlled to be 20%, and the required viscoelastic solid electrolyte glue solution is obtained after stirring for 10 hours. And (3) taking the cut positive pole piece, and uniformly coating the glue solution on the surface of the positive pole piece by using a wire rod, wherein the coating thickness is controlled to be 10 micrometers. Similarly, a layer of glue solution is coated on the surface of the negative pole piece, and the coating thickness is controlled to be 12 μm. And then placing the pole piece coated with the viscoelastic electrolyte glue solution at 80 ℃ for vacuum drying for 6 hours to obtain the modified pole piece.
Example 4
This example provides a method for preparing a viscoelastic electrolyte modification layer:
weighing the following raw materials in parts by mass: succinonitrile 65%, PPC substrate 5%, LiBOB 30%. The raw materials are dissolved in N, N-dimethylformamide, the solid content is controlled to be 17%, and the required viscoelastic solid electrolyte glue solution is obtained after stirring for 13 hours. And (3) taking the cut positive pole piece, uniformly coating the glue solution on the surface of the positive pole piece by using a wire rod, and controlling the coating thickness to be 5 microns. Similarly, a layer of glue solution is coated on the surface of the negative pole piece, and the coating thickness is controlled to be 7 μm. And then placing the pole piece coated with the viscoelastic electrolyte glue solution at 65 ℃ for vacuum drying for 8 hours to obtain the modified pole piece.
Example 5
This example provides a method for preparing a viscoelastic electrolyte modification layer:
weighing the following raw materials in parts by mass: succinonitrile 45%, PVC substrate 15%, LiODFB 40%. The raw materials are dissolved in N-methyl pyrrolidone, the solid content is controlled to be 8%, and the required viscoelastic solid electrolyte glue solution is obtained after stirring for 12 hours. And (3) taking the cut positive pole piece, and uniformly coating the glue solution on the surface of the positive pole piece by using a wire rod, wherein the coating thickness is controlled to be 8 microns. Similarly, a layer of glue solution is coated on the surface of the negative pole piece, and the coating thickness is controlled to be 10 μm. And then placing the pole piece coated with the viscoelastic electrolyte glue solution at 75 ℃ for vacuum drying for 10 hours to obtain the modified pole piece.
Example 6
In this example, the solid content was changed to 3% instead of 13%, and the other conditions were the same as in example 1.
Example 7
In this example, the solids content was replaced by 15% with 13%, and the other conditions were the same as in example 1.
Example 8
In this example, the surface coating thickness of the positive electrode sheet was changed to 6.5 μm and 2 μm, and the other conditions were the same as in example 1.
Example 9
In this example, the surface coating thickness of the positive electrode sheet was changed from 6.5 μm to 11 μm, and the other conditions were the same as in example 1.
Example 10
In this example, the surface coating thickness of the negative electrode tab was changed to 9 μm and 4 μm, and the other conditions were the same as in example 1.
Example 11
In this example, the surface coating thickness of the negative electrode tab was changed from 9 μm to 13 μm, and the other conditions were the same as in example 1.
Comparative example 1
In this comparative example, the mass fraction of succinonitrile was replaced with 43%, the mass fraction of the polymer substrate was replaced with 25%, the mass fraction of the lithium salt was replaced with 32%, and the other conditions were the same as in example 1.
Comparative example 2
In this comparative example, the mass fraction of succinonitrile was replaced with 67%, the mass fraction of the polymer substrate was replaced with 13%, the mass fraction of the lithium salt was replaced with 20%, and the other conditions were the same as in example 1.
Comparative example 3
In this comparative example, the mass fraction of the polymer substrate was replaced with 3%, the mass fraction of succinonitrile was replaced with 65%, the mass fraction of the lithium salt was replaced with 32%, and the other conditions were the same as in example 1.
Comparative example 4
The comparative example was carried out under the same conditions as in example 1 except that the mass fraction of the polymer substrate was replaced with 27%, the mass fraction of succinonitrile was replaced with 45%, and the mass fraction of the lithium salt was replaced with 28%.
Comparative example 5
This comparative example did not prepare a viscoelastic electrolyte modification layer and the assembled cell structure is shown in fig. 2.
The viscoelastic electrolyte modification layers of examples 1 to 11 and comparative examples 1 to 4 were prepared in an all-solid battery prepared as follows:
preparing a positive pole piece: and uniformly mixing and stirring 90 wt% of lithium iron phosphate, 5 wt% of conductive carbon black, 5 wt% of polyimide and NMP to obtain uniform anode slurry with the solid content of 50%. And then uniformly coating the slurry on the surface of an aluminum foil of the positive current collector, and drying, rolling and the like to obtain the required positive pole piece 1.
Preparing a negative pole piece: and mixing and stirring 90 wt% of silica negative electrode material, 5 wt% of carbon nano tube and 5 wt% of polyvinyl alcohol with NMP uniformly to obtain negative electrode slurry. And then uniformly coating the slurry on the surface of the copper foil of the negative current collector, and drying, rolling and the like to obtain the required negative pole piece 2.
Assembling the battery cell: the positive electrode modified pole piece containing the viscoelastic electrolyte modified layer 3, the negative electrode modified pole piece containing the viscoelastic electrolyte modified layer 3, and the polymer solid electrolyte (solid electrolyte 4) film prepared in examples 1 to 11 and comparative examples 1 to 4 were prepared into a laminated core by a zigzag lamination machine.
Cell solidification: and standing the battery cell clamp for 24 hours to ensure that the viscoelastic solid electrolyte modification layer can be uniformly attached to a pole piece/electrolyte interface, and carrying out formation, aging and capacity grading to obtain the required all-solid-state battery. In which the structure of the all-solid battery composed of the viscoelastic interface modification layers in examples 1 to 11 and comparative examples 1 to 4 is shown in fig. 3.
The positive pole piece and the negative pole piece adopted by the battery cell in the comparative example 5 and the solid electrolyte are the same as those in the examples 1 to 11 and the comparative example.
The cells assembled from the above cells comprising the viscoelastic interface modification layers of examples 1-11 and comparative examples 1-4 and comparative example 5 were tested for discharge capacity and lithium ion conductivity, and the test results are shown in table 1:
TABLE 1
Figure BDA0003354754690000131
Figure BDA0003354754690000141
From the above results, it can be seen from comparative examples 1 to 5 that succinonitrile has the best effect when used together with a PEO substrate, the highest cell discharge capacity, and the highest ion conductivity of the modified layer. Comparing example 1 with examples 6 to 7, it can be seen that the solid content greatly affects the flowability of the glue solution, and the uniformity and integrity of the modified layer formed under the condition of inappropriate solid content are poor, which is not beneficial to improving the performance of the battery cell. Comparing example 1 with examples 8 to 11, it can be seen that the coating thickness of the modification layer has a large influence on the performance of the battery cell, the modification layer cannot uniformly cover the surface due to too low coating thickness, the ion transmission channel is difficult to construct, and the internal resistance is increased due to too high coating thickness, which prevents the lithium ions from being rapidly transmitted at the interface. Through comparative examples 1-4, it can be seen that the succinonitrile and the polymer substrate account ratio have a large difference in the cell performance, and improper account ratio can result in too high or too low glue fluidity, and thus a film cannot be formed on the surface of the pole piece, and therefore the construction of the modification layer cannot be realized. Comparative example 5 the cell did not work at all without the modification layer, indicating the importance of the modification layer.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims (10)

1. The viscoelastic electrolyte modification layer is characterized by comprising, by mass, 45-65% of succinonitrile, 5-25% of a polymer substrate and 20-40% of a lithium salt.
2. The viscoelastic electrolyte modifying layer of claim 1, wherein the polymeric substrate comprises any one or a combination of at least two of PEO, derivatives of PEO, PMMA, derivatives of PMMA, PVDF, derivatives of PVDF, PPC, derivatives of PPC, PVC or derivatives of PVC.
3. The viscoelastic electrolyte modifying layer of claim 1 or 2, wherein the lithium salt comprises LiTFSI, LiFSI, LiPF6LiBOB, LiODFB or LiClO4Any one or a combination of at least two of them.
4. A method of producing a viscoelastic electrolyte modifying layer according to any one of claims 1 to 3, comprising:
adding the raw materials of the viscoelastic electrolyte modification layer into an organic solvent for mixing to obtain a viscoelastic electrolyte glue solution;
and respectively and independently coating the viscoelastic electrolyte glue solution on the surfaces of the positive pole piece and the negative pole piece, and respectively and independently obtaining viscoelastic electrolyte modification layers on the surfaces of the positive pole piece and the negative pole piece after drying.
5. The production method according to claim 4, wherein the organic solvent comprises any one of acetonitrile, N-dimethylformamide, acetone, chloroform, anisole or dichloroethane or a combination of at least two thereof;
preferably, the raw material of the electrolyte modification layer accounts for 5-20% of the solid content of the organic solvent.
6. The method according to claim 4 or 5, wherein the mixing speed is 500 to 1000 rpm;
preferably, the mixing time is 10-15 h.
7. The preparation method according to any one of claims 4 to 6, wherein the coating thickness of the surface of the positive electrode plate is 3 to 10 μm;
preferably, the coating thickness of the surface of the negative pole piece is 5-12 μm.
8. The method according to any one of claims 4 to 7, wherein the drying temperature is 60 to 80 ℃;
preferably, the drying time is 6-12 h.
9. An all-solid battery comprising the viscoelastic electrolyte modification layer according to any one of claims 1 to 3;
preferably, the all-solid-state battery comprises a positive electrode plate containing the viscoelastic electrolyte modification layer, a negative electrode plate containing the viscoelastic electrolyte modification layer and a solid electrolyte.
10. Use of a viscoelastic electrolyte modification layer according to any one of claims 1 to 3 in the field of lithium ion batteries.
CN202111347490.9A 2021-11-15 2021-11-15 Viscoelastic electrolyte modification layer and preparation method and application thereof Pending CN114069041A (en)

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